In an IP network for communication using Internet Protocol, and further in a mobile communication network using Mobile-IP (MIP. Refer to HYPERLINK http://www.ietf.org/rfc/rfc3220.txt), a mobile terminal (hereinafter referred to as mobile node MN) consisting of a portable personal computer, a portable telephone terminal, or the like is connected to the Internet through a home agent HA functioning as a node. In such a network, mobile node MN informs the corresponding home agent HA about the location information of each mobile node MN, so that the location of each mobile node is registered in each home agent HA.
The location information received from mobile node MN is maintained and managed in each home agent HA as binding cache BC. Home agent HA transfers a packet, which is originated in correspondent node CN and destined for mobile node MN, in accordance with the contents of binding cache BC.
When the location of mobile node MN is registered into correspondent node CN for optimizing the route, correspondent node CN transmits a packet for transfer directly to mobile node MN of interest according to binding cache BC.
The above-mentioned procedure is also applicable in the case of Mobile-IPv6 (MIPv6. For example, refer to http://www.ietf.org/internet-drafts/draft-ietf-mobileip-iPv6-18.txt).
Mobile-IPv6 is a kind of Mobile-IP which is based on Internet Protocol version 6.
Further, the above-mentioned procedure is also applicable to Hierarchical Mobile-IP (HMIP. For example, refer to http://www.ietf.org/internet-drafts/draft-ietf-mobileip-hmiPv6 -06.txt) and its IPv6 version, Hierarchical Mobile-IPv6 (HMIPv6. For example, refer to http://www.ietf.org/rfc/rfc2460.txt). These protocols enable to support high-speed handover by a Mobility Anchor Point (MAP), which is implemented in the network to which the mobile node moves, and acts as a proxy node in place of home agent HA.
The following links respectively refer to aforementioned nonpatent documents:
In such a mobile communication network, home agent HA acting as a node, correspondent node CN and mobility anchor point MAP maintain and manage the location information reported from mobile node MN as binding cache BC, thus enabling packet transfer from correspondent node CN to mobile node MN.
Under such circumstances, when a failure occurs in either node which retains binding cache BC registered from mobile node MN, transferring a packet originated in correspondent node CN and destined for mobile node MN is suspended even when the node of interest is restored from the failure, unless binding cache BC having been retained is restored.
Generally, when a failure occurs in a node retaining binding cache BC, the restoration of binding cache BC relies on a request for location re-registration which is to be issued at an arbitrary timing from mobile node MN. In such a case, a packet originated in correspondent node CN and destined for mobile node MN possibly fails to reach the destination, or reaches through an unintended route (in other words, through a route which is not optimized).